Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$102.42	9.295%	$111.9399	$111.94	$111.95	$111.90
Purchase #2	$35.71	3.778%	$37.0591	$37.06	$37.05	$37.10
Purchase #3	$174.41	8.865%	$189.8714	$189.87	$189.85	$189.90
Purchase #4	$121.93	13.641%	$138.5625	$138.56	$138.55	$138.60
Purchase #5	$82.53	3.254%	$85.2155	$85.22	$85.20	$85.20
Purchase #6	$47.30	5.324%	$49.8183	$49.82	$49.80	$49.80
Purchase #7	$72.93	4.263%	$76.039	$76.04	$76.05	$76.00
7 purchase totals =	$637.23		$688.5057	$688.51	$688.45	$688.50